Effect of cyclosporine A in erythema nodosum leprosum.

Erythema nodosum leprosum (ENL) is a reactional state of lepromatous leprosy in which the loss of suppressor cell function, decrease in suppressor cell numbers, and increase of interleukin 2 production are observed. We reasoned that cyclosporine A (CsA), by opposing these immune responses, could suppress the ENL reaction and restore patients to the quiescent lepromatous state. We tested this hypothesis in vitro by measuring the effect of CsA on M. leprae-triggered suppressor cells. In 24 of 25 patients with ENL, suppressor cell activity was restored by CsA. The target of CsA appeared to be macrophages. These findings are significant in that they provide the first evidence for the potential efficacy of CsA in the treatment of ENL. Preliminary clinical trials indicate a beneficial therapeutic effect associated with increased T suppressor cells in lesions.